The invention relates to an apparatus for the fixed-angle fixation and compression of a fracture site or osteotomy of a bone.
EP 1 255 498 B1 makes known a bone plate which can be used either for compression or fixation to treat bone fractures. This is achieved by this known prior art in that the bone plate has a top side, an underside intended for contact with the bone, and a plurality of holes for receiving bone screws, these holes being located along the longitudinal axis of the plate and connecting the top side and the underside, wherein at least one of the holes is composed of a combination of a circular hole having an elongated hole. The distance between the centers of symmetry of the circular hole and the elongated hole is shorter than the sum of the radius of the circular hole and half of the longitudinal axis of the elongated hole. An elongated hole as defined by this known prior art is an oval, ellipsoidal, or rectangular hole, or a combination of such shapes as an elongated hole, but circular holes are excluded.
This known prior art can generate either only compression or fixation. Compression is attained by way of longitudinal displacement of the fracture elements when the bone screw is tightened in the elongated hole. It does not simultaneously bring about fixed-angle fixation, however. This can be attained only by using a separate bone screw in another elongated hole, and so a large number of bone screws must be used. Treatment of the fracture is complex and complicates the patient's surgery.
Furthermore, DE 31 13 639 A1 makes known an osteosynthetic compression plate comprising a plurality of slot-type holes located in the longitudinal direction of the plate, the holes comprising contact surfaces for countersunk bone screws having a spherical head. The compression of the fracture is achieved here by way of a displacement motion of the two bone parts, wherein the spherical head of the countersunk bone screw glides in the longitudinal direction of the plate along a conical or spherical countersink within the slot-type holes. A further bone screw is used for fixation in the position that has been compressed in this manner. This prior art therefore does not differ from that mentioned previously.
WO 02/096309 A1 describes a bone plate for fixing fractures of the proximal humerus, comprising a stem-shaped part, the length of which is greater than the width thereof, and a spoon-shaped part, the width of which is greater than the width of the stem-shaped part, wherein the stem-shaped part and the spoon-shaped part have a common longitudinal central axis. The holes in the stem-shaped part comprise a combination of a hole having a larger diameter and a hole having a smaller diameter, wherein at least one of the screw holes has an at least partial internal thread.
Simultaneous compression and fixation within a screw hole is likewise not possible with this known prior art.